The only reasonable conclusion is that the source -- or trail of sources -- is even more incriminating than the fake documents. Why else would Heyward and Rather allow the CBS news division to commit slow, public suicide?
I think that you hit the nail on the head with this one.
And while CBS has 1st Amendment legal precedents ensuring that a libel lawsuit brought against it would be very difficult to win, the same cannot be said of their sources.
Any "source" who is openly repudiated as having given CBS false and defaming counterfeit documents is in DEEP legal trouble, which leads me to think his daughter is tied in with it (his daughter being a Dem party activist in Texas)